code: def ref_grad_spectral_norm_no_output_u(
      w, u, dy, dim, itr, eps, test, output_u, need_grad_flags
  ):
      return ref_grad_spectral_norm(
          w, u, dy, None, dim, itr, eps, test, output_u, need_grad_flags
      )
  
file_path: nnabla/python/test/function/test_spectral_norm.py
imports: import pytest
  import numpy
  import nnabla
  import nnabla.functions
  import nnabla.parametric_functions
  from nbla_test_utils import list_context
label_desc: Use image node_id 3 for calling a global function with example usage: ref_grad_spectral_norm_no_output_u(w, u, dy, dim, itr, eps, test, output_u, need_grad_flags) and returns: ref_grad_spectral_norm